Will post pictures up shortly, none handy ATM.
Barn find 1983 ATC110. Located in Lenox, Michigan.
Would make a fun and simple restoration project, or use it for parts to revive another bike.
A lot of solid pieces on it that are probably difficult to find.
The OEM rear master cylinder is a tried and true system. A lot of guys who build expensive, frame up drag bikes use OEM. I recommend going that route. That's a genuine answer to your question, and I'm not trying to be a salesman, but I have an entire OEM rear brake setup for sale if your interested.
Facts^^^^, If your building from scratch with top shelve parts, you can get above $20,000 quick. You wanna go deep in the game, you can get to $30,000.